NXD63B100

The Siemens NXD63B100 is a ‑pole,  amp molded case circuit breaker from Siemens’ NXD family, engineered for heavy‑duty low‑voltage power distribution and protection. Designed to provide dependable overcurrent and short‑circuit protection in 120/208 VAC and 277/480Y VAC three‑phase systems, the breaker is well suited for large commercial, industrial, and utility applications. Typical uses include feeder protection, main service disconnects, motor control centers, and sub‑feeds in distribution panels where both high current capacity and robust fault handling are required. Its ‑pole configuration ensures simultaneous disconnection of all phases under fault or overload conditions, supporting NEC compliance and system safety.

Electrically, the NXD63B100 incorporates a thermal‑magnetic trip unit, which combines long‑time overload protection with instantaneous magnetic response to short‑circuit events. The breaker is UL 489 listed with a high interrupting capacity (AIC) suitable for commercial power systems, allowing it to safely interrupt large fault currents typical of high‑capacity feeders and service entrances. This thermal‑magnetic design helps distinguish between harmless inrush currents (such as those from large motors or transformers) and actual overcurrent conditions, reducing nuisance trips while maintaining reliable protection. The 1200 amp continuous rating positions the NXD63B120 as a main or feeder breaker in large panelboards and switchboards.

Mechanically, the NXD63B100 features a rugged molded case housing and a manual toggle or lever actuator that provides clear ON/OFF indication and a straightforward reset after a trip event. Its design accommodates standard industrial conductor sizes and integrates with Siemens panelboard and switchboard bus systems configured for high‑amp bolt‑on breakers. The breaker’s standardized footprint and accessory compatibility (such as auxiliary contacts, shunt trips, and handle ties) allow engineers and installers to tailor protective control schemes to project requirements. With its combination of high current capacity, reliable trip performance, and proven Siemens quality, the NXD63B100 is a strong choice for demanding three‑phase protection needs.

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